Ticks, a summer nuisance, are now spreading to areas previously unaffected. This expansion poses new hazards to human health. Some regions have long dealt with ticks, but their reach is broadening.

William Brangham talked with Holly Gaff, a mathematical ecologist at Old Dominion University, about these blood-feeding pests. Gaff studies tick behavior and ecology, aiming to understand their growing prevalence.

Brangham is an experienced correspondent and producer at PBS News Hour. He also hosts a program called Horizons. Solveig Rennan, a national affairs producer for PBS News Hour, contributed to this discussion.